FBI has informants in Wikileaks and Terabytes of internal documents and hard-drives from 2009-2017.

I've read the Wikileaks-chat that was leaked by Emma Best. Wikileaks really hated Hillary Clinton. They wanted her to lose at all costs. They didn't like Trump either, but he was a minor blip on their radar. In 2016, their whole ressources were rerouted to a single project: Sabotaging Hillary Clinton.
(Julian Assange later admitted that they had damaging info on Trump, but that it was pretty tame compared to the already-known scandals of 2016 and not worth the effort of publishing it.)

My guess:
Wikileaks bit off more than they could chew. They were too greedy and allowed themselves to become accomplices in Russia's operation to hack the Democrats and leak their files. The hacked emails were what they had been looking for all along.

How complicated is Wikileaks' situation? To this day, Julian Assange refuses to either confirm or deny that they got the DNC-emails from Guccifer 2.0.
(Which is pretty suspicious. If they didn't get them from Guccifer 2.0, that would better their situation. So why is Wikileaks keeping the option alive that they DID get the emails from Guccifer 2.0?)

The alleged offenses in the complaint notwithstanding, the government has an abundance of data to work with: over a dozen WikiLeaks’ computers, hard drives, and email accounts, including those of the organization’s current and former editors-in-chief, along with messages exchanged with alleged Russian hackers about DNC emails. Through a series of search warrants, subpoenas, equipment seizures, and cooperating witnesses, the federal government has collected internal WikiLeaks data covering the majority of the organization’s period of operations, from 2009 at least through 2017.

...

Publicly released and leaked documents from Assange and his legal team allege that several laptops and hard drives belonging to the organization were intercepted by an intelligence agency during this time period. According to an affidavit from Assange, “three laptops ... assorted electronics [and] additional encrypted hard drives” were taken along with his suitcase in late September 2010. Assange’s legal team produced several additional affidavits and supporting documents detailing the existence and disappearance of the suitcase. The suitcase contained at least five hard drives, all of which were encrypted, according to Assange. However, the government has had eight years to guess or recover the passwords or break the encryption on the hard drives. Several other drives, numerous emails, and at least one cooperating witness may have aided in the process.

...

Soon after the arrest and cooperation of Hector Xavier Monsegur, a.k.a. Sabu, his hacking group (LulzSec) made contact with WikiLeaks. Sabu and LulzSec would become some of WikiLeaks’ most significant sources. ... Communications between Sabu and WikiLeaks were monitored by the FBI. And some of the group’s communications with others were later seized in their arrest or turned over by Sigurdur Thordarson, a WikiLeaks volunteer who became an informant for the FBI that August.

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In addition to briefing the FBI in a series of meetings, Thordarson reportedly provided them with thousands of pages of WikiLeaks chat logs. Further, in March 2012, Thordarson allegedly provided the FBI with eight WikiLeaks hard drives containing up to 1020GB of data, according to a purported FBI document. Officials have not confirmed the authenticity of the document, though the amount of data provided is corroborated by additional sources. In an interview with Ars Technica, Thordarson claimed that Icelandic authorities had seized an additional 2 TB of WikiLeaks-related data from him, which he assumed was then shared with the U.S. American and Icelandic authorities had previously cooperated on Thordarson’s case and portions of the WikiLeaks investigation. According to leaked letters from WikiLeaks’ legal team, at least some of the hard drives had belonged to Assange. Thordarson’s debriefings and the hard drives of up to 3 TB of data may have contained the decryption keys or passwords needed to decrypt the hard drives Assange alleged had been seized earlier.

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Ultimately, at least some messages between WikiLeaks and the “Guccifer 2.0” were obtained by the U.S. government, although the method of communication for those messages remains unconfirmed.

According to what’s informally known as “the GRU indictment,” WikiLeaks sent Guccifer 2.0 a message on June 22, 2016. The message instructed Guccifer 2.0, a persona the U.S. government believes was used by Russian operatives, to send new material to them so it would “have a much higher impact.” On approximately July 6, the organization sent another message encouraging Guccifer 2.0 to send “anything [H]illary related” in time for the Democratic National Convention, which WikiLeaks thought Clinton would use to solidify support. The quoted portion of the exchange ends with WikiLeaks saying they thought conflict between Sen. Bernie Sanders and Clinton would be “interesting.”